Telephone system



Feb. 27, 1940.

B. F. LEWIS TELEPHONE SYSTEM Filed March 3, 1939 3 Sheets-Sheet 1 //VVENTOR Bf. LE W/S Feb. 27, 1940. a. F. LEWIS TELEPHONE SYSTEM FiledMarch 3, 1939 3 Sheets-Sheet 2 Q (H QN I I1 l\l III a. I 3 M H R Q. 1 8N@ m V 8 8 V R an I IN I W 6? /N VENTUR B. F. LE WIS 1 A TTOR/VEY Feb.27, 1940. B. r. Laws TELEPHONE SYSTEM 3 Sheets-Sheet 3 Filed March 3,1939 3 6 NON- L INEAR EL EMENT I la- ML Q E K n m A WM 7 u J r k JP A?4U HNUUHHUUU T U U HF H 9 8 w w W T FIG. 7

Patented Feb. 2'7, 1940 nunirso sT ArEs hirer rricn vclaims. (01.179-16) This invention relates totelephone systems, and particularly tosignal sending and receiving arrangements' in automatictelephonesystems;

It isan object of the present invention, to im 5 prove and simplifymechanisms for transmitting,

receiving and recording digit designations; I

f Another object is, to employ designations that are comparativelyfreefrom line disturbances.

Heretotore systems have been employed: in which digit designations haveconsistedof: har monies of a fundamental frequency specially selected torepresent telephone designations, and i different methods havebeenproposed for recording these designations.

vide means for representing digit designations by harmonics modified asto energy levels, each digit comprising a combination of signals; and;the various signals comprising harmonics that are modifiedasto theirenergy levels. j

Ancther feature of the'invention is to provide a'receiving and recordingmechanism for said signals including thermionic tubes biased. tobecomevactive in response to corresponding signals and recording meanscontrolled by said tubes to record the signals as corresponding digitdesignations. v .v

The invention has. been: illustrated inrthe accompanying drawings inwhich Figs. 1 to 7 show various detailsaof an impulse transmittingmechanism. and recording the invention. 7 I

Of these figures, Fig. 1' shows a general assembly of the transmitterwith certain" portions of the housing removedi Fig. 2- shows thecommutator drums" and brushes to modify circuits to produce digitimpulses;

Fig. 3 shows details of a locking device for the 40 drums; I I v 4, 5and 6 show variousdetails; of the brush and contact arrangementsiindifferent positions;

Fig. '7 shows the arrangement of the contact elements on a drum; and

Fig. 8 shows a diagrammatic representation of digits. tension 5 on theright side thereof on which the. digits are marked}, and in the housingI there Itis a feature of the present invention to'prodevices inaccordancewith separated sufiiciently to provide insulating por- "tionsbetween them and between the rows. The

width of the contacting elements is practically equal to the insulationspaces between the four r0ws, as shown in Fig. '7. At the right-hand endof each drum there is provided a handle 4 that projects through anopening 5 in the housing i and bymeans. of which the drums may be set inthesetting of the drums to select eight succeeding Each drum is. alsoprovided with an exis a. window for each drum such as window 8' solocated inv relation to the legends on the drum that when the drumsaremoved, the legends will be visible through the windows. At the top ofthe housing i there aretlocated two springs'ii and. Iii for each drumthat always engage two special contact strips on the drum so that nomatter in what positions the drums are set, these. brushes 9 and, Itwill always connect with certain contact elements. The contact stripsmay be. connected by any suitable means such as connecting wires in themanner shown in Fig. '7 to establish diiTe-rent combinations ofconnections between the contact elements-and the brushes 9 i or ill asdetermined by the setting of the drums.

The purpose of these connections will becomef apparent as'thedescription proceeds. At the edge of the extension ti of each drum thereare a number of notches it as illustrated in Fig. 3 one-of which'may beengaged by a" projection I2 for each drum- These projections extend froma 3 bar I3 operated by a lever, arrangement Hi and held by a spring I5in such a position that all drums are locked bythe projections i2engaging the notches II inthe drums. The lever may be connected by. anysuitablemeans such as the bar to the switchhock in the regular telephoneset ,at the subscribers station so that when the receiver is on theswitchhook the bar ii is depressed and moves lever It and bar I3 toremove the projections i2 from notches H to permit-the drums to berotated for the setting of the various digits. [At the bottom of thehousing I there 'is locateda brush carriage arrangement comprising arack 28 anda pinion 2i engaging-this rack and v rotatably secured at oneend by means of a shaft 22 to adisc23fslidably mounted on bar 24'. Therackj20f and bar 2 3v are" supported at both ends of the housing insuitable bearings such 'as 25 at one end and 26 at the other. The shaft'22 extends into a housing 30 and is connected to the inner end of aspiral spring 32, the other end of which is connected to the housing 33.This housing in turn is connected by the supports 33 and 34 to the disc23. On disc 23 there is mounted a 3 bracket 35 supporting a lever 36having a knob 38 extending outside of the housing I through 1 a slot 40.The disc 23 also supports the flexible brush member 42 which isinsulated from the 1; disc 23 but is provided with a brush 44 for en-'gagement with the drums as will be described hereinafter. This member42 has an extension 46 that engages the end 41 of the lever 36. The

purpose of these parts, as illustrated in Figs. 4 to 6 in detail, is toprovide means whereby the brush 46 may be swept transversely over thedrums in succession when the drums have been set. Attached to the disc23 is also three pairs of spring contacts 56, 5! and 52 that areoperated by a lever 53 as will hereinafter be described. This lever isactuated by a projection 54 attached to thehousing near the left-handend thereof.

Another pair of contacts 55 are operated bya lever 56. This lever isactuated by the two pro- J'ections 58 and 59 in succession. The contactsengages the various slots ll indrums 2 to lock 1 them in actuatedpositions. The subscriber then listens to dial tone which is produced aswill presently be described. When dial tone is heard the subscriberengages the knob 38 of the lever release the knob 38 and the tension ofthe spring 36 and rotates this lever on its pivot to disengage the brushM from contact with the drums and then moves the lever, the disc 23 andthe associated apparatus towards the left looking at Fig. 1. This willrotate the ratchet 2! on the rack 20 and thus cause the spring 32 to bewound up in the housing 30. When the subscriber has moved these partsall the way towards the left, he will 32 will then return the parts tonormal as the spring 32 will act on the pinion 2| to rotate it back overthe rack 20. A speed governing device (not shown) may be employed toregulate the speed at which the pinion is rotated back over rack 20. Assoon as this mechanism is released the brush 44 will contact with andsweep over the drums transversely and engage the contact segments asencountered. It should however be.

noted that immediately after the disc 23 left the normal position thelever 53 will be engaged by the projection 54 and this lever 53 willthereby be swung over in an operative position toward the right asillustrated in Fig. 4 to cause the springs 50 t0 be closed, 5! to beopened and 52 to be closed. Immediately after the disc starts on itsreturn to normal lever 56 will be engaged in succession by projections58 and 59, as illustrated in Fig. 5, thus causing the contacts 55 to beopened-twice in succession. When the disc-23 has completely returned tonormal the lever 53 will be returned to normal position by engaging theprojection 54 and thus restore the springs 50, 5|

and 52 to normal position. When the conversation is completed theswitchhook is replaced which causes the bar ll, lever M, bar l3 andprojections 12 to be restored to release the drums. The drums'may thenbe returned to normal as left in the positions in which they have beenset a as desired.

In Fig. 8 the impulse sending mechanism. described above has beendisclosed in diagrammatic form showing drums 2 with contacts 9 and i6engaging them, the lever 36 and the contacts 53,

as will. hereinafter be described. The line from the subscribers set ismarked 66 and extends to a line finder 61 which has been shown "in dia-.grammatic form. The line finder may be connected to a registering device68 shown below the dash-dotted line. This registering deviceincludes anumber of difierent circuits and apparatus such as the filter 69,amplifier-detector and gain control devices 10, vacuum tubes H and 12, asteptacts 55'and 62, the transmitter and the right-' hand winding ofinduction coil 63 and causes the line finder 61 to connectthe callingline 36 to a central ofiice sender in the. usual manner. This connectionthen extends over leads 18 to a first selector-which has not been shownas apparatus of that kind is well known in the art. However, prior totheextension of a connection over this first selector operations may takeplace in any manner'well known in the art to establish over leads 18 aconnection through the usual sender connector to the registeringapparatus 68. When this connection is made the-relay 86 is operated inany well-known manner toprovide certain locking circuits as willhereinafter be described. Relay 83 is also operated over the directcurr'ent circuit now established from'battery and ground through thewindings of this relay, the tip and ring connection through conductors13, line finder 61, conductors 66, contacts 55, the lower set of theswitchhook contacts 62, the transmitter and the right-hand winding ofinduction coil 63. Relay 83 in operation closes a circuit for relay 84which looks to ground at contacts of relay. 80.

The purpose of relay 84 will become apparent as the descriptionproceeds. It should also be noted that alternating current from thehundred cycle source 85 is now also connected back to the calling line.The resistance 83 is inserted in series with source 85 to limit thevolume of the current from this'sourceso as to make it suitable as adial tone for the subscriber's receiver.

The contacts 9 and IQ of the various drums are connected to certaincontact elements of the drums as seen in Fig. 7. When the subscriberhears the dial tone the transmission of the selected digits may begin.To this end the subscriber will now engage the knob 38 of lever 36 andremove. the brush 44 from connection with the drums and move the brushcarriage all the way towards the left and then release the lever 38 atwhich time the brush 44 engages the first drum ready for thetransmission of the impulses as determined by the settings of thesedrums. The first efiect, however, of the movement of the carriagetowards the left is that the projection 54 will engage the lever 53 toclose contacts 59 and 52 and open contacts .51, then when the carriagestarts on its return to normal, the contacts 55 will beopened twice insuccession by the projections 59, 59 to open the connection to theregister 68. The immediate result of the first opening of the connectionbetween contacts 55 is that the direct current connections completed onthe'removal of the receiver from the switchhook opens the circuit frombattery and ground through the windings of relay 83 over the conductors19 and 66. The release of relay 83 closes the circuit for relay 81 frombattery, winding 01? this relay and contacts of relays 83 and 84 toground. Relay 88 is also operated on the release of relay 83 over acircuit from battery, winding of this relay and contacts of relays 89,83 and 84 to ground. When relay 83 operates after the first operation ofthe connection at contacts 55, relay 89 will be operated from battery,winding of relay 88, contacts of this relay and relay 81, winding ofrelay 89 to ground at relay 84. Relay 8! is slow in releasing so it doesnot release at this time. When the relay 93 releases in response to thesecond opening of the contacts 55, relay 9!! will operate from batterythrough the winding of this relay, contacts of relays 89 and 83 toground at relay 84. Relay 99 in operating", removes ground at its outerright-hand armature and back contact to enable the tubes H and I2tooperate as will be described hereinafter. This relay also closes ashunt across the'resistance 86 and consequently the full effect of thealternating current from the hundred cycle source at 85 is transmittedback over the line. Relay 99 looks to ground and contacts of relay 3 3.

Now it should be observed that the next step will be that the brush 44will proceed to travel transversely over the drums in succession andcontact with the segments in accordance with the setting of the drums.However, before the brush M engages any contact segment of the firstdrum, it touches insulation and there is no connection through contacts9 and Hi to brush Consequently, at this time the non-linear element 65is shunted across the left-hand winding of the induction coil 93 inplace of the receiver and receives the hundred cycle energy from theline by the transformer action of the induction coils 63 and 92. Thenon-lineal characteristics of element 65 cause this energy to betransformed into certain harmonics which are transmitted back to theline by. the induction coil. The eifect of this transmission is aided bythe condenser 93. These harmonics are transmitted back over the'line ata certain normal energy level. The arrangement in register 68 is suchthat these harmonics willcause the switch 13 to take one step each timethey are applied to the register after the circuit begins to functionand'it is for that purpose that they are applied to the line before thebrush 44 engages each row of segmentsin each drum. These harmonies arethen modified by the segments encountered 'on the drums in their varioussettings to either be reduced in their energy levels to an intermediatevalue or be extinguished to produce,'as will hereinafter be explainedthree difpractically negligible value.

vferent effects. To effect the two last-mentioned energy levels thenon-linear element may either be partially shunted by connecting oneside of this element through the brush 44 tocertain contact elements inthe drum through the brush [0 and the resistance 94. This producesharmonies ofv an energy level lower than the normal level. ment may bedirectly shunted by a connection established by the brush 44 throughcertain other contact elements in the drum and brush 9. This reduces theenergy level of the harmonics to a It is by combinations of thesevarious harmonic outputs that digits may be built up and it will now bedescribed how this is effective in register 68'.

It should now be observed that normally there may be applied a positivepotential by the am plifier-detec-tor and gain control devices 19 in anymanner well known in the art to the grids v96 and 91 over the conductor98 and individual resistances 9.9 and l99.- This normal potential iseffective to operate the two tubes "ii and 12 as soon as relay 99 isoperated as described by the removal of ground on lead 98 at the outerright-hand armature and back contact of this relay. The cathodes of thetwo tubes are biased at different negative potentials by being connectedat different points as shown on the potentiometer circuit at I9], sothat tubes H and 'lz'will operate depending on difierent values of thepotential existing on the conductor 93. Such values are first the normalpositive potential from the amplifier-detector and gain control devices.19 which causes the tubes to become active, and second a medium negativepotential and third the maximum negative potential. The three values ofthe potentials which, of course, are caused by a direct currentsource inthe devices 19 are modified normally by the harmonics of the highestenergy level harmonic, harmonics of a lower intermediate energy leveland harmonics of negligible value. It should be stated here that thefilter 69 is such that only the harmonics are transmitted to the devicesl9 and the fundamental hundred cycle current is eliminated fromthese'devices and also that the ground connection at contacts of relay99 when released causes the normal potential applied to conductor 99 tobe such that both tubes H and T2 are actuated. Hence when as statedabove, relay 99 is operated and the harmonics transmitted from thesubscribers station when the non-linear element is not shunted by eitherof the circuits through the brushes 9 or H), these harmonics are of thehighest energy level. Thus devices 19 will change its positive potentialto become of a maximum negative potential so that both tubes will becomeinactive or extinguished whereas if the harmonics of a lowerintermediate value are transmitted through the shunt circuit over brushI0 and due to the potentiometer ltll the potential will be changed to anintermediate negative potential so only tube H will remain active andtube 12 become inactive. However, when the ele ment 65 is completelyshunted by the circuit over brush 9, the harmonics transmitted will notbe of sufficient strength to materially change the positive potential onlead 98 and thus both tubes will again become active. These variousconditions are brought about due to the travel of the brush 44 over thedrums and thus as a result of these various potentials on conductor 98,the tubes will either be both inactive, that is, when On the other handthis non-linear elefull strength harmonics are ,transmitted' and tube Hremain active when harmonics of a lower intermediate level aretransmitted or both tubes will be active when practically no harmonicsare transmitted. With this in mind, it is evident that combinationsof'such various harmonics may be produced to compose digits so thatbefore. the

, brush engages the first row of segments on any drum, both tubeswill-become inactive and when the brush engages the succeeding four rowsof segments on any drum either one or both tubes will become active, andwhen the brush engages the insulation between the rows of segments onany drum both tubes .will become inactive. As for example if. the digitJKL or 5, referring to Fig. 7, is the one that the brush M will engage,it is evident thatwhen the brush engages the first segment aconnectionwill .be established through brush it; when it engages the correspondingsegment'in the second row, a circuit will be established through brush9; when the brush A l engages the segment in the third row, a circuitwill be completed through brush 9 and when the brush 44 engages thesegment inthe fourth row a circuit will be completed through brush ill.Thus, for .the first segment in the first row only tubell will beactive; for the second row both tubes will .be active; for the third rowboth tubes Will be active and for the fourth row only tube ill will beactive, whereas when'the brush passes between these rows of segments,both of the tubes will become inactive.

With this in mind it is evident that the output circuit of the tubes Hand '12 will when current flows through these circuits cause theoperation of relays I62 and H33. As stated normally these outputcircuits are activeand consequently relays liiZ and 193 will beenergized and when the full harmonics are first applied both tubes willbecome inactive. Consequently these two relays I62 and i513 willrelease. The release of these relays closes circuits for the twowindings of the magnet "M which causes the brushes of the switches is totake one step. The next action will be that only tube 7| will remainactive and relay 32 will release. This produces no effect. That is, thefirst register relay in group 15 will not be operated as there is nocircuit closed through the brush and first contact of switch 13 to thisrelay. Then, both tubes will become inactive and relays I02 and H13 willbe both released, causing the magnet M to energize the switches '53 totake a second step. Then both tubes will become active and relays IE2and H33 will be operated. In this case the second register relay of thegroup i5 will operate over acircuit from battery, winding of this relay,the second contact and brush of switch 13 to ground at relay I03. Thenboth tubes will become inactive causing the switch to take a third step.Then both tubes will become active, causing relays m2 and H23 to beoperated. The operation of relay I03 in this case closes a circuit for athird register relay over the brush and the third contact of switch 73.Then tubes H and 12 will become inactive causing the switch to take afourth step. Then tube H only remains active and at this time noregister relay will be actuated as there will be no circuit to thisrelay through the brush in the fourth contact of switch 13. Hence bysending this digit 5 the second and third register relays only will beoperated. 'Iheseregister relays will lock in operated position by aground applied at relay 8d. In the same manner seven other digits may beregisteredby the settingof the other combination, ,as hereafter shown.It will be noted that in-this register there would be thirty-two relays,four relays for each digit and all been set in accordance with the eightdigits suitable-apparatus will be provided whereby the settings of theregister willbe employed for selecting connections beyond to the calledsubscribers line and when the register has performed its functions, therelay 8B will be released and the register relays restore to normalandalso the relays 84, 90, 89, 87 and 88 and the register circuit itselfwill be removed from the connection leading to the first selector in anymanner well known in the art. v 7

What is claimed is:

1. In a telephone system, a line, means for transmitting over said linegroups of signals, each group representing a telephone digit and eachsignal comprising a number of harmonics of a fundamental frequencymodified asto their energy levels to identify the digits, and meansresponsive to said groups of signals for recording the digitsrepresented thereby. I

2. In a telephone system, a line, a source of alternating currentconnected to said line, means for producing harmonics of alternatingcurrent from said source at fixed energy levels, means for transmittingsignals representative of telephone designations over said linecomprising combinations of impulses of said harmonics at said fixedenergy levels and at other modified energy levels, and means responsiveto said combinations of impulses for making records representingcorresponding telephone designations.

3. In a telephone system, a line, means for.

transmitting over said line groups of signals each group representing atelephone digit and each signal comprising a number of harmonics of afundamental frequency modified as to their energy levels to identify thedigits, thermionic tubes associated with said line operated in responseto the succeeding signals in each group in corresponding combinations,and means responsive to current through said tube when operated to makea record representing a telephone digit as determined by said groups ofsignals.

4. In a telephone system, a line, a source of alternating currentconnected to said line, means vfor producing in said line. signalscomprising harmonics of said alternating current, means for changing theenergy levels of the harmonics in said signals from a normal level totwo succeeding lower levels, means for combining signals of harmonics ofthese various energy levels into codes, each representative of atelephone designation, andmeans responsive to said combinations ofsignals for recording the corresponding telephone designations.

5. In a telephone system, a line, a source of alternating currentconnected to said line, means for producing in said line signalscomprising harmonics of said alternating current, means for changing theene gy levels of the harmonics in said signals from a normal level totwo succeeding lower levels, means for combining signals of harmonics ofthese various energy levels into codes, each representative of atelephone desig nation, recording means, and, means for suppressingcurrent from said alternating current source and for transmitting thecode signals to said recordingmeans to record the telephone designationsrepresented by them.

6. In a telephone system, a line andmeans for transmitting over saidline groups of signals, each group representing a telephone digit andeach signal comprising a number of harmonics of a fundamental frequencymodified as to their energy levels to identify the digit, and aplurality of three-element thermionic tubes, means for transmitting saidsignals to the control'elements of said tubes, and means associated-Withthe cathode and anode elements of said tubes for controlling thedischarges thereof to cause said tubes to discharge'at differentpotentials on their respective control elements as established thereonby said harmonics of difierent energy levels, and recording meansresponsive to discharges from said tubes to record said signals as digitdesignations. 1

7. In a telephone system, a line, a source of alternating currentconnected to said line, means for producing in said line signalscomprising harmonics of said alternating current, means for changing theenergy levels of the harmonics in said signals from a normal level totwo succeeding lower levels, means for combining signals of harmonics ofthese various levels into codes, each representative of a telephonedigit designation,

a plurality of three-element thermionic discharge devices, means fortransmitting said codes in succession to the control elements of saiddevices and preventing current from said alternating current source frombeing transmitted to said control elements, and means associated with acathode and anode elements of said devices for controlling thedischarges thereof to cause said devices to discharge at differentpotentials on their respective control elements as established thereonby said harmonics of difierent energy levels, and means responsive todischarges from said devices for recording said codes as digitdesignations.

BENJAMIN F. LEWIS.

